Report: Dark energy quickens universe expansion

magnify the box   A supernova explosion 10 billion light-years away, located in the box, suggests that dark energy is hastening the expansion of the universe

April 2, 2001
Web posted at: 4:46 p.m. EDT (2046 GMT)

In this story: 'Finding the Loch Ness monster' Midlife crisis for the universe RELATED STORIES, SITES

By Richard Stenger
CNN

(CNN) -- Besides indicating that the universe is expanding much faster than in the past, the chance discovery of the most distant supernova has revived a discarded theory of Albert Einstein suggesting the pervasive existence of mysterious dark energy.

Astronomers using the Hubble Space Telescope found the exploding star about 10 billion light-years from Earth.

The discovery bolsters the startling notion that the universe has recently begun speeding up its expansion, which scientists first speculated three years ago based on the unusually dim light from other distant supernovas.

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Cosmic graphics: Hubble illustrations help explain the expansion of the universe

"It shows that the expanding of the universe is really speeding up and not slowing down as conventional astronomers had thought for 70 years," University of Chicago astronomer Michael Turner told reporters on Monday.

The new stellar explosion has helped astronomers understand how the universe expands, "much the same way a parent follows a child's growth spurts by marking a doorway," said Hubble scientist Adam Riess, lead researcher in the new study.

'Finding the Loch Ness monster'

The supernova appears brighter than it should if the universe had been growing at a steady rate, astronomers said. It reveals that the universe slowed down its expansion for a time and then began a period of accelerated growth, Riess said.

Riess and colleagues sifted through countless Hubble pictures to search for the supernova, first identified in 1997.

Supernova explosions are so powerful that they can be visible across the universe, but so brief they last only about six months. Spotting it in several Hubble test observations over time proved an astonishing feat.

"It was like finding the Loch Ness monster in a photo," said Anne Kinney, director of NASA's Origins Program.

Supernovas serve as cosmic measuring sticks for astronomers, who calculate the age of the universe in part based on the distance of such stellar explosions.

By looking at the light from this particular supernova, for example, they see an event that actually took place 8 billion years in the past when the universe was a relative infant. Scientists estimate the age of the cosmos at 12 billion to 15 billion years

Midlife crisis for the universe

According to the new theory, gravity slowed the rate by which the universe expanded after the Big Bang until the cosmos reached half its current age.

Billions of years ago the attractive force of gravity was then overtaken by the repellant force of dark energy, the main ingredient in the cosmos, which began pushing galaxies away from each other at increasing speed.

Scientists know little about the force, which Einstein postulated, then dismissed, in the early 20th century, other than its gravity is repulsive and it is spread out smoothly between galaxies.

But some consider it a Holy Grail in the quest to understand the universe. Discussing dark energy, astronomers speak of hidden dimensions, particles living on borrowed time and the grand unification theory of forces.

"I can sum it up in one phrase. This is very weird stuff," Turner said.

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NASA
Space Telescope Science Institute

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